1. Field of the Invention
The present invention relates generally to a spring-assisted cordless roller shade without clutch system, and more particularly to a roller shade including an assembly of a connector, a central shaft, a subsidiary shaft, a fixing member, a torsion spring and a constant force belt spring module for controlling rolling/unrolling of the shade and locating the shade.
2. Description of the Related Art
A conventional shade locating/controlling device is applied to a shade or the like and assembled with a rotary shaft. The shade locating/controlling device and the rotary shaft are mounted in a tubular housing. The shade locating/controlling device cooperates with a bead chain drive seat, a locking device and springs to control the rolling/unrolling of the shade. For example, a conventional skill discloses a shade locating/controlling structure. The other conventional skill discloses a shade damping structure capable of freely locating and releasing the shade in any position.
As well known by those who are skilled in this field, the bead chain system for rolling/unrolling the shade is dangerous to children. To overcome this problem, an improved bead chain structure has been developed. For example, another conventional skill discloses a cordless shade rolling/locating structure.
With respect to the structural design of the roller shade control device, the conventional device also employs a clutch mechanism to control the rolling/unrolling operation of the shade and locate the shade. In general, the assembling structure of such system is relatively complicated so that more installation steps are required and the installation time is increased. Moreover, in operation, it is harder to truly control the rolling or releasing position of the shade. Especially, with respect to a roller shade with longer rolling/releasing travel, when the rolling travel gets close to the top end portion, it often takes place that the rolling force is insufficient.
As well known by those who are skilled in this field, in the case that the roller shade necessitates a longer rolling/releasing travel, it is necessary to arrange a torsion spring with greater action force to control the roller shade in cooperation with a clutch mechanism providing a locking effect so as to overcome the activation force of the torsion spring. As a result, a user needs to apply a greater force to the shade for releasing the shade from the locking effect of the clutch. In addition, it is necessary to repeatedly pull the roller shade many times so as to adjust the roller shade to a desired position. This is not what we expect.
In conclusion, the conventional shade controlling/locating structure and the relevant assembling components thereof have some shortcomings in use and structural design that need to be overcome. It is therefore tried by the applicant to provide a spring-assisted cordless roller shade without clutch system to eliminate the shortcomings existing in the conventional shade controlling/locating structure so as to change the use form and practically widen the application range thereof. For example, in condition of easy operation and simplified structure, in comparison with the conventional shade controlling/locating structure, the spring-assisted cordless roller shade without clutch system of the present invention is free from the bead chain system of the conventional shade controlling/locating structure so that the security in operation of the roller shade is ensured. The spring-assisted cordless roller shade without clutch system of the present invention improves the shortcomings of the conventional shade controlling/locating structure that it is necessary to employ a clutch mechanism and the installation of these mechanisms is troublesome and the operation of the roller shade is laborious.